1. Field of the Invention
The present invention relates generally to substrate and semiconductor wafer preparation systems and methods, and more specifically to a re-circulation system for chemicals and deionized water used in substrate and semiconductor wafer scrubbing systems.
2. Description of the Related Art
In the fabrication of semiconductor devices, there is a need to perform wet cleaning of substrates at various stages of the fabrication process. The wet clean is designed to wash away any by-products of the fabrication process, remove contaminants, and to achieve and maintain the necessary degree of cleanliness essential to proceed to a subsequent fabrication operation. In some cases, the wet clean itself is a fabrication step, and the plurality of tools used for wet cleaning, scrubbing, buffing, etching and the like use such fluids as dionized water (DI water) for rinsing, and a plurality of chemicals supplementing cleaning, scrubbing, polishing, buffing, or otherwise processing wafers according to processing needs.
Similarly, in the fabrication of hard disk drives, cleaning operations are needed to maintain a clean and smooth disk substrate. Residue or contaminants remaining on substrates in the fabrication of hard disks and other devices utilizing similar substrates is likewise unacceptable, and various rinsing, scrubbing, buffing, and the like tools are used for periodic cleaning, scrubbing, and rinsing operations, and using DI water and other chemicals for the desired processes.
Substrate cleaning and scrubbing techniques, methods, and apparatus are plentiful and known in the art, and incorporate such operations as rinsing and scrubbing, immersion, as well as the application of thermal, mechanical, chemical, electrical, or sonic energy. One known cleaning and scrubbing technique implements brush stations in which polyvinyl alcohol (PVA) brushes are used to scrub both active and back sides of a substrate. Materials other than PVA may be also employed in scrubbing operations. In a typical brush station process, a substrate is rotated in a vertical or horizontal orientation by substrate drive rollers, also called substrate edge wheels. As the substrate is rotated, a pair of cylindrical brushes or pads are brought into contact with the opposing surfaces of the wafer. The brushes or pads are mounted on counter-rotating mandrels disposed on opposite sides of the wafer being processed. The mandrels span the diameter of the substrate across the substrate center. The rotation of the mandrels rotates the cylindrical brushes or pads which are then applied against the opposing surfaces of the rotating substrate. During the scrubbing operation in some systems, nozzles direct sprays of liquid, e.g., an abrasive slurry, a chemical solution, or a rinse solution, on the opposing surfaces of the wafer. In some applications, liquid for polishing, scrubbing, or cleaning is supplied through the brush or pad, and some systems employ a combination of nozzles and fluid delivery through the brush or pad. In order to maintain the PVA brushes in a condition useful for substrate processing, fluids need to be supplied through the brush, or dispensed on the surface of the brush, either continuously or periodically with only short interruptions whether the brush is being used for processing a wafer or is in an idle state or mode.
As can be appreciated, scrubbing tools such as a typical brush box consume a large quantity of water and other chemicals. A typical dual-brush scrubbing tool implementing through-the-brush dispensing of chemicals for processing or DI water for rinsing and using PVA brushes consumes approximately two to four liters per minute of dispensed fluid during operation. Processing tools and systems currently in use supply the selected DI water and/or chemicals to the system or tool for use, and then drain the consumed fluids to waste.
In view of the foregoing, there is a need for substrate brush station preparation systems and methods that incorporate re-circulation of chemicals and DI water used in substrate processing and/or in the maintenance of the tool, station or system.